Strength of recommendation
Grade 1 (strong)
Terminology: “We recommend . . .”
Grade 2 (weak)
Terminology: “We suggest . . .”
Quality of evidence
Level A (high quality)
Source of evidence: Well conducted randomized trials
Level B (moderate quality)
Source of evidence: Less rigorous or inconsistent randomized trials
Level C (low or very low quality)
Source of evidence: Observational studies, case series, and unsystematic observations or expert opinion